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Introduction

A simple, inexpensive and non-invasive method for assessing the mineral supply for horses over a longer period of time would be highly desirable. One possibility could be to measure the minerals in the hair instead of having a costly blood sample taken by a vet. Especially as the blood only shows the current status, and not over the last few weeks or months. Many values in the blood are regulated within very narrow limits, so that the blood count does not necessarily allow a statement to be made about the mineral supply to the cells and tissues.

Results of human medicine

Several laboratories now offer ‘hair mineral analyses’. But are these really useful and can I rely on them?

In human medicine, there are only reliable results for methylmercury, arsenic and lead

Let’s first take a look at human medicine. There, hair mineral analyses have long been standard in terms of alcohol, medication, or drug abuse, but caution should be exercised when detecting heavy metal contamination and the result should be checked again using other methods. Only a few heavy metals can be clearly attributed to excessive intake due to their specific chemical form, e.g. methylmercury from the consumption of products containing fish.

Where do measured values come from?

Minerals and heavy metals are often also stored externally

The first critical point in analysing hair minerals is to differentiate between minerals that are actually stored in the hair and those that have been transferred to the hair by external factors. Minerals are not only found in the feed and therefore in the horse’s metabolism, but also in various care products from shampoo to fly repellent and coat shine products. Possible residues from manure, bedding or sweat as well as from environmental pollution – especially if there are factories manufacturing goods near by.

Once the sample has arrived at the laboratory, it is subjected to various washing and degreasing processes. It is unclear to what extent the minerals that have been transferred to the hair by external factors are dissolved in the cleaning process it is therefore impossible to say whether my horse is actually well supplied with magnesium, for example, or whether the magnesium measured merely comes from my horse shampoo. In this case, special analyses would have to be carried out to determine exactly what form the element is in and whether it has entered the hair via external or internal factors. Such analyses are extremely time-consuming and expensive and are not carried out for horsehair mineral analyses.

Reference values must be standardised

The reference values are also not yet standardised. Reference values are usually formed in laboratories by the most frequently measured values in a certain range, but this does not necessarily reflect the values of healthy, non-symptomatic horses.

Horse coat and grooming kit
Hair mineral analyses are by no means comprehensive
© Adobe Stock/ lichtreflexe

If you look at the current literature, there are studies on the detection of heavy metal or environmental pollution via hair and also initial attempts to define standardised limit values. However, these always fail due to the extreme variability that is already naturally found in hair.

The mineral content of horsehair naturally fluctuates between 5 – 35%.

It also changes with the colour and age of the hair, with the time of year, with the place on the body from which the hair sample was taken, with the length of the hair and so on. Even if you take hair samples from the same horse in the same way over and over again and the horse is constantly and evenly supplied with a mineral feed, you will find extreme fluctuations within a year. We cannot yet say how much of this is simply due to the natural seasons and how much is due to possible metabolic stress. However, it shows that simply analysing minerals from hair and comparing them with some reference values taken from the literature does not necessarily say anything about the actual mineral status.

Conclusion

To summarise, there is still a lot of research to be done before this method can be used reliably and meaningfully to determine the mineral requirements of horses. It remains to be seen whether it can ever be used to measure a horse’s mineral supply over the course of the last few months.

For the detection of toxic heavy metal exposure, a urine or blood test should always be used in addition to the hair mineral analysis in order to rule out external factors.

What already works very well – in addition to genetic analyses based on pulled horsehair – is the determination of cortisol in hair and thus the stress level of the horse. These measurements are increasingly being used in research to draw conclusions about the well-being of the animals. It will probably be some time before this method becomes an established standard in reliable diagnostics.

Scientific evidence and sources:

  1. Fazio, F., Gugliandolo, E., Nava, V., Piccione, G., Giannetto, C., & Licata, P. (2020). Bioaccumulation of mineral elements in different biological substrates of athletic horse from Messina, Italy. Animals, 10 (10), 1877.
  2. Giannetto, C., Fazio, F., Nava, V., Arfuso, F., Piccione, G., Coelho, C., … & Licata, P. (2022). Data on multiple regression analysis between boron, nickel, arsenic, antimony, and biological substrates in horses: The role of hematological biomarkers. Journal of Biochemical and Molecular Toxicology, 36(2), e22955.
  3. Kalashnikov, V. V., Zaitsev, A. M., Atroshchenko, M. M., Miroshnikov, S. A., Zavyalov, O. A., Frolov, A. N., & Kurilkina, M. Y. (2021, March). Reference intervals of essential and toxic elements concentrations in mane hair and blood serum of Arabian purebred horses. In IOP Conference Series: Earth and Environmental Science (Vol. 677, No. 5, p. 052084). IOP Publishing.
  4. Madkour, F. A., & Abdelsabour‐Khalaf, M. (2022). Performance scanning electron microscopic investigations and elemental analysis of hair of the different animal species for forensic identification. Microscopy Research and Technique.
  5. Mazzola SM, Colombani C, Pizzamiglio G, Cannas S, Palestrini C, Costa ED, Gazzonis AL, Bionda A, Crepaldi P. Do You Think I Am Living Well? A Four-Season Hair Cortisol Analysis on Leisure Horses in Different Housing and Management Conditions. Animals (Basel). 2021 Jul 20;11(7):2141. doi: 10.3390/ani11072141. PMID: 34359269; PMCID: PMC8300697.
  6. Fabian, D., Baumgartner, M. R., & Koller, M. F. (2016, June). Sinn und Unsinn von Haaranalysen. In Swiss Medical Forum (No. 22, pp. 466-471). EMH Swiss Medical Publishers.

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